Dry-mixed detergent compositions



United States Patent 3,360,469 Patented Dec. 26, 1967 ABSTRACT OF THEDISCLOSURE Dry-mixed built detergent compositions of a granular,compacted sodium tripolyphosphate having a specified density andparticle size and having distributed on it 2.5 to 7% of water, togetherwith at least one of a watersoluble, non-soap synthetic anionic ornonionic detergent, a sodium silicate, a chlorocyanuric compound,chlorinated trisodium phosphate, an alkali carbonate and an inertorganic filler, are provided.

This invention relates to dry-mixed built detergent compositions, andparticularly to such compositions which contain as an essentialcomponent fast-hydrating, dense sodium tripolyphosphate builder in aform in which it is readily soluble without caking under adversedissolving conditions.

Built detergent compositions useful in automatic washing machines,dishwashers, sanitizing applications, bleaching applicaticfis and thelike are available irrtablet, granular and liquid forms. The tablet andgranulaiiorms have particular advantage because they are easily handledand stored as compared with the liquid materials, and because with themit is not necessary to ship and store water as is the case with liquidcompositions. This invention is concerned with the dry compositions,namely the tablet and granular varieties.

These dry compositions generally contain sodium tripolyphosphate as abuilder and any or all of an anionic or nonionic surfactant, ananti-corrosion agent such as sodium silicate, a chlorinated cyanuriccompound such as trichlorocyanuric acid, dichlorocyanuric acid or a saltof dichlorocyanuric acid, chlorinated trisodium phosphate, an alkalicarbonate and an inert inorganic filler such as sodium sulfate, sodiumchloride, sodium orthophosphate and the like. The surfactant and thesodium tripolyphosphate are the principal cleaning components,

while the sodium silicate prevents the alkaline detergent from attackingmetallic parts of washing machines and the like with which it comes intocontact when dissolved in water in use. The chlorinated cyanuriccompound serves as a sanitizing and bleaching agent and the filler isemployed as an extender to obtain the desired bulk density and toprovide smoother tablets and more uniform compositions. The makeup ofthe compositions depends on the ultimate use to which they will be put.

There are basically two methods of preparing these dry compositions. Onemethod involves forming an aqueous slurry of the sodium tripolyphosphateand other ingredients, while the other method simply involvesdry-blending the ingredients and either using them directly as granularcompositions or tableting them. The dry-blending system has the obviousadvantage of ease of operation in not requiring drying, for examplespray-drying, to provide the final product.

A serious problem is inherent in dry-blending compositions, however,which is not as aggravated in forming the compositions from slurries.Sodium tripolyphosphate, an essential constituent of these compositions,is erratic in its dissolving characteristics. Its dissolution in waterin end use or in some cases in subsequent processing sometimes isslowed, and the material even cakes into inso- "veses if entrappedtemporarily in a piece V "iproperly agitated, such as might occurwashing machine ger upon pouring the granular ntiiiner of water withoutagitation. ion. compositions containing more than about 759' f sodiumtripolyphosphate frequently cake in water. is problem is particularlyaggravated in dry-mixed compositions, whose preparation does not exposethem to water. When the compositions are prepared in water, a tendencyin the sodium tripolyphosphate to give serious trouble in dissolving onuse in a composition into i Even absent s'ucha of the composition, oftenshows up during preparation of the composition.

In an attempt to overcome this unpredictable and serious dissolvingproblem, as well as to provide a dense sodium tripolyphosphate ofregular particle size, H. L. Marschall et al., provided a method ofproducing a sodium tripolyphosphate having a density of about 1.0 to1.25 g./cc., and a desirable hydration and dissolving rate. Their methodcomprises compacting the sodium tripolyphosphate at a high pressure intoa large, dense mass of the material, and grinding this mass to theproper particle size. This is taught in the Marschall et al. US. patentapplication, Ser. No. 289,315, filed June 20, 1963 and assigned to theassignee of this invention.

The dense, granular sodium tripolyphosphate provided by Marschall etal., referred to hereinafter as compacted sodium tripolyphosphate, has afaster rate of dissolution in water under normal conditions, than doessodium tripolyphosphate not produced by their method. However, it hasnot been found in practice to solve all problems relative to dissolving.While under normal conditions it dissolves in water more readily thandoes noncompacted sodium tripolyphosphate, there are certain adverseconditions, for example when a composition contains on the order of 75%or more of sodium tripolyphosphate or when the composition is notagitated when added to water or is temporarily entrapped such as in apiece of clothing in a washing machine or in a dispenser of the kindused for example in a home dishwasher, which cause it to cake and notdissolve despite its normally fast dissolving characteristic.

It therefore has remained desirable, and it is an object of thisinvention, to provide a sodium tripolyphosphate which not only has afast dissolving rate under normal dissolution conditions, but also whichdissolves readily without caking under adverse conditions.

I have now found it possible to provide an improved form of compactedsodium tripolyphosphate which produces dry-mixed built detergentcompositions which dissolve readily without caking under normal, andalso under adverse, dissolving conditions. The improved compacted sodiumtripolyphosphate of my invention is provided by uniformly distributingon a compacted sodium tripolyphosphate containing 0 to 0.7% by weight ofwater, an

amount of water to increase the amount of water in the tripolyphosphateto 2.5 to about 7%, and preferably 2.5 to 4%, by weight. This improvedmaterial is then drymixed in a composition containing by weight about 20to of my sodium tripolyphosphate and any or all of 0 to 50% of awater-soluble, non-soap organic synthetic detergent which may be ananionic or nonionic detergent, about 0.5 to 50% of sodium silicate, 0.5to 20% of a chlorocyanuric compound, 0.5 to 50% of chlorinated trisodiumphosphate, 0.5 to 50% of an alkali carbonate and 0.5 to 60% of an inertinorganic filler. The components present in a given composition vary asthe compositions end use varies, and a variety of combinations of theseadded ingredients in practice are used with my improved sodiumtripolyphosphate. These compositions may be granular, in which case theyare produced by simply mixing the components together, or in tabletedform, in,which case the granular compositions are tableted underpressure. Throughout the specification and in the claims appendedhereto, reference to compositions as being drymixed means compositionswhich are not slurried or dissolved in a liquid in compounding, andwhich are free-flowing, solid compositions. The 2.5 to 7% of water in myimproved compacted sodium tripolyphosphate obviously does not causecompositions prepared from it to be removed from this dry-mixedcategory.

For some reason which is unknown to me, sodium tripolyphosphate whichhas not been compacted by the process of the Marschall et al. patentapplication referred to above to produce a uniform sodiumtripolyphosphate product having a density of about 1.0 to 1.25 g./cc.,does not respond to addition of moisture in the above amounts at all inthe same fashion as does the compacted material. It is most surprising,therefore, that it is possible to effect the herein improvement ofdry-mixed built detergent compositions by employing in them compactedsodium tripolyphosphate treated in accordance with my invention.

The improved sodium tripolyphosphate employed in preparing thecompositions of my invention is produced from the Marschall et al.compacted material in accordance with my invention by exposing it to ahumid atmosphere, preferably while the sodium tripolyphosphate is influidized state, by spraying water into the tripolyphosphate while thelatter is undergoing agitation or the like. The amount of water presentin the sodium tripolyphosphate is analyzed by heating the sodiumtripolyphosphate at 150 C. for one hour and observing the weight lossproduced thereby. Normally the moisture content of the compacted sodiumtripolyphosphate before treating is about to 0.7% depending onconditions encountered in preparing the material and in storing it.

I have found the minimum amount of water required to be present in thecompacted sodium tripolyphosphate to provide a material useful inproviding the herein highly soluble compositions to be quite critical,as shown by a so-called caking test. This test involves placing a gramsample of the sodium tripolyphosphate in granular form in a porcelaincrucible (Coors No. 2) and carefully adding 6 ml. of distilled water tocompletely cover the tripolyphosphate. The tripolyphosphate is thenprobed gently with a dissecting needle at 10 second intervals, and thetime at which caking (the formation of a hard mass of material) occursis noted.

The dependence on its water content of the ability of compacted,granular sodium tripolyphosphate to withstand caking and the specificityof this property to compacted tripolyphosphate are demonstrated inTables 1 and 2 which follow:

TABLE 1.CAKING TIME OF COMPACTED GRA'SULAR SODIUM TRIPOLYPHOSPHATE[Particle size 20 +100 mesh, U.S. Standard] TABLE 2.CAKI'NG TIME OFNON-COMPACTED GRANU- LAR SODIUM THIPOLYPHOSPHATE 1 -20 +100 mesh,produced by rotary calcining.

Caking times of on the order of 300 seconds or more are indicative of aproduct which will dissolve readily in use, regardless of the existenceof adverse conditions.

In preparing the dry-mixed, built detergent compositions of myinvention, the principal ingredient, the compacted sodiumtripolyphosphate containing the herein amount of water, is measured intothe detergent formulation in amount sufficient to constitute about 20 toby weight of the composition. Preferably it has a particle size of about-16 to mesh with no more than about 20% being 70 mesh.

A surface active agent, which may be either anionic or nonionic, also isdesirable in many compositions. Certain cationic surfactants cannot beemployed because they are incompatible with the compacted sodiumtripolyphosphate. When used the surfactant is added to the mixture inthe amount of about 0.5% to 50% by weight of the composition.

A sodium silicate having an Na O to SiO, mole ratio of about 1:1 toabout 1:3.2, in amount of about 0.5 to 50% by weight may be included inthe formulation also as an anti-corrosion agent and for its building andalkaline properties. The mole ratio of M 0 to SiO in the silicatedetermines its alkalinity; as the ratio approaches lzl the sodiumsilicate becomes more alkaline. Ratios below 123.2, for example 1:4,dissolve too slowly and are not effective.

Another ingredient which is often useful in these formulations is achlorocyanuric compound, which may be trichlorocyanuric acid,dichlorocyanuric acid, or the alkali metal or alkaline earth metal saltsof dichlorocyanuric acid, exemplified by sodium dichlorocyanurate,potassium dichlorocyanurate, calcium dichlorocyanurate and the like.These materials, which serve as sanitizing and bleaching agents, aresolids and are available in granular form. When used they generally areemployed in amounts of about 0.5 to 20% by weight. Another usefulchlorinated compound is chlorinated trisodium phosphate which may beused in an amount of 0.5 to 50% as a sanitizing agent.

The alkali carbonates are also useful additives for many formulations,Typical carbonates are sodium sesquicarbonate and sodium carbonate,which are useful in an amount of about 0.5 to 50%.

Inert inorganic fillers also may be employed in these compositions.Typical fillers include sodium sulfate, sodium chloride, sodiumorthophosphates and the like. Where used they control the bulk densityof the composition and improve the surface appearance and strength oftablets containing them.

In addition, small amounts of auxiliary compounds such as sodiumcarboxymethyl gellulose normally in an amount of to 1.5%, foamstabilizers such as lauroyl diethanolamide, tarnish inhibitors,fluorescent brighteners, perfumes, bacteriostats, coloring matter andthe like may be employed in my compositions. Where it is desired toemploy the compositions as granular mixes they are merely packaged intheir mixed form. Where it is desired to form them into tablets, theyare uniformly mixed and then compressed into tablets. The pressingnormally is carried out at a pressure of on the order of 100 to 350p.s.i., and the finished tablet has a bulk density in the range of about0.8 to 1.3, The tablets normally have strengths (when pressed on edge)of about 10 to 15 pounds or more. If the tablets are suitably aged forat least 24 hours, they have a strength (when pressed on edge) of up toabout 25 pounds.

Anionic surfaceactiveagents are useful in my formulation in amdiTnfsmffrom about 0.5% to about 50% by weight. These anionic surface activeagents are non-soap synthetic detergents made up of water-soluble saltsof organic sulfuric reaction products having from about 8 to about 18carbon atoms in the form of a straight-chain or branched chain alkylradical or an acyl radical within the molecular structure and containingsulfuric or sulfonic acid ester radicals. Typical examples of theseanionic surface active agents are sodium or potassium alkyl benzenesulfonates or sodium or potassium alkyl sulfates or sulfonates in whichthe alkyl group, which may be straight or branched chained, containsfrom about 8 to about 18 carbon atoms, eg., sodium dodecyl benzenesulfonate, sodium tridecyl benzene sulfonate; the sodium and potassiumalkyl glycerol ether sulfonates, including ethers of higher fattyalcohols derived from the reduction of coconut oils; the reactionproducts of isethionate; sodium or potassium alkyl sulfonates andsulfates obtained by sulfonation of coconut or tallow fatty alcohols andmixtures of such alkyl sulfates; dialkyl esters of sodium or potassiumsalts of sulfosuccinic acid; sodium or potassium salts of sulfates orsulfonated monoglycerides, e.g., those derived from coconut oil; sodiumor potassium salts of higher fatty alcohol esters of sulfocarboxylicacids, e.g., sodium salt of lauryl alcohol ester of sulfoacetic acid;and other anionic agents set forth in US. Patent 2,486,921 issued toByerly on Nov, 1, 1949. If desired, the anionic surfactant can be addedin the form of a dense, dry bead or as a flake admixed with sodiumsulfate. In this latter case, the sodium sulfate constitutes a portionof the total sodium sulfate used in making up the entire mixture.

The nonionic surface active agents Useful in the present inventionare'non-soap synthetic detergents made up of a water solubilizingpolyoxyethylene group in chemical combination with an organichydrophobic compound. Among the hydrophobic compounds which can be usedare poly-oxypropylene, the reaction product of propylene oxide andethylene diamine, aliphatic alcohols, etc.

Examples of nonionic synthetic detergents useful in the presentinvention are, condensation products of 6 to 30 moles, and preferably 7to 11 moles, of ethylene oxide with 1 mole of an alkyl phenol containing6 to 12 carbon atoms in the alkyl group; condensation products of 6 to30 moles of ethylene oxide with 1 mole of an aliphatic straight orbranch chained alcohol containing 8 to 18 carbon atoms; condensationproducts of ethylene oxide and the reaction product of propylene oxideand ethylene diamine', nonyl phenol polyethoxy ethanol (commerciallyknown as Triton N" series); isooctyl phenol polyethoxy ethanol(commercially known as Triton X series). Another well known group ofnonionic detergents is marketed as Pluronic series. These compounds arethe reaction products obtained by condensing ethylene oxide with ahydrophobic base produced by the condensation of propylene oxide withpropylene glycol, and have molecular weights on the order of about 1800.The addition of polyoxyethylene radicals to the hydrophobic baseincreases the water solubility of the nonionic detergent and concurrent-.ly increases the foaming properties of the detergent in aqueoussolution in proportion to the mole ratio of polyoxyethylene radicals tothe hydrophobic base. In general, a surfactant which has a mole ratio of7.5 moles of ethylene oxide per mole of an alkyl phenol, e.g., nonylphenol, is low-foaming while one with a mole ratio of :1 foamsmoderately. The molecular weight of these nonionic synthetic detergentswill range from as low as 800 up to about 1 1,000.

Nonionic surfactants should be employed in the herein compositions inthe amount of about 0.5 to by weight of the total composition or abovein order for the surfactant to be completely effective. Amounts over 15%should be avoided because the nonionic surfactant tends to exude ing awater content of 3%.

6 or oil out of the detergent formulation when it is pressed intotablets. Within the range of 0.5 to 15% the nonionic surfactant giveseffective washing action, and has been found to be effective as a binderfor the remainder of the detergent formulation without oiling out" ofthe pressed tablet.

The following examples are presented by way of illustration of thisinvention only, and are not to be considered as limiting the scopethereof in any way. All amounts are present by weight.

Example 1.Tablets A compacted sodium tripolyphosphate having a densityof 1.2 g./cc. and a particle size of 20 +100 mesh was treated with waterby spraying while the sodium tripolyphosphate was being agitated toprovide a material hav- This material was stirred together with anamount of anionic spray dried beads to provide a -10% by weighttripolyphosphate-anionic spray dried bead granular mixture. The beadswere composed of 41.9% of sodium tridecyl benzene sulfonate, 0.9% ofcarboxymethyl cellulose, 36.4% of sodium sulfate, 8.2% of sodiummetasilicate and 12.6% of sodium chloride. This mixture of the sodiumtripolyphosphate and the beads was then compacted into tablets having adiameter of 1% inches and a thickness of 1 inch, and weighing 50 grams.

A corresponding tablet was prepared in the same way from compactedsodium tripolyphosphate which had not been provided with the 3% ofwater, but rather was used with its initial amount of 0.5% of water.

The two tablets were placed in one-half inch wire mesh cages placed in afixed position in a top-loading automatic home washing machinecontaining 16 gallons of agitated F. tap water. The tablet containing mywater-treated compacted sodium tripolyphosphate disintegrated in 71seconds and entirely escaped from the cage, while a 9.9 gram core orcake of the tablet containing the compacted sodium tripolyphosphate nottreated in accordance with my invention remained after 5 minutes in thewasher.

The same kind of comparative results was obtained when samplescontaining 78% of sodium tripolyphosphate and the balance the anionicspray dried bead were tested, thus demonstrating that my water treatmentof compacted sodium tripolyphosphate is effective in compositionscontaining both amounts of tripolyphosphate. These amounts are in therange in which sodium tripolyphosphate dissolution is erratic.

Example 2.Tablets Tablets containing 55 parts by weight of sodiumtripolyphosphate and 45 parts of the anionic spray dried beadcomposition used in Example 1 were prepared and tested in the same wayas were the tablets of Example 1. The tablets prepared with mywater-treated compacted sodium tripolyphosphate disintegrated completelyand left the cage in seconds. The tablet prepared with the compactedsodium tripolyphosphate which was not water treated in accordance withmy invention required 167 seconds to disintegrate and leave the cage.

Examples 3 to 6 Granular compositions having the formulations shown inTable 3 which follows, were prepared by dry mixing the indicatedingredients until homogeneous mixtures had been obtained. The examplesidentified by the letters A through D are comparative examples run withordinary compacted sodium tripolyphosphate not treated in accordancewith my invention. The compositions are given in Table 3 together withresults of dissolution tests run with them, under conditions which wouldnormally lead to caking. The test involved dropping a IO-gram sample ofeach composition into an individual beaker containing one liter of waterat the indicated temperature. The composition was permitted to sit inthe water for one minute before agitation with a magnetically-operatedstirrer was commenced. The ease of dispersion was noted. The granularcompositions normally were of a particle size to pass through a meshscreen and be retained on a 200 mesh screen, with the individualcomponents varying within this range.

4. The composition of claim 1 in which the dry-mixed, built detergentcomposition is in the form of a granular composition.

5. A method of producing dry-mixed built detergent compositionsessentially containing compacted sodium tripolyphosphate and beingreadily soluble in water without TABLE 3.DISSOLVING PROPERTIES OFGRAN'ULAR DETERGENT FORMULATIONS CONTAINING SODIUM TRIIOLY- PHOSPHATEWITH AND WITHOUT TIIE WATER TREATMENT OF THIS INVENTION LaundryDetergent Hard Surface Machine Dish- Hand Dishwashing Cleaner washingDetergent Detergent Ex. 3 Ex. A 1 Ex. 4 Ex. B 1 Ex. 5 Ex. C Ex. 6 Ex. D

Composition, Wt. Percent:

compacted Sodium 'Iripolrphosphate (3'); water) compacted SodiumTripolyphosphate (anhydrous) Anionic Spray Dried Beads 01 Example 1.

, Disodium Phosphate. "'Sodium Sesquiearbouate. Sodium Carbonate SprayDried Beads (40% alkyl benzene sullonate, 60%

sodium sulfate} II- Sodium Metasilicate Sodium DiehlorocyanurateLow-foaming N onionic Surfactant (Polyetho lated isooct phenol withterminal isobutyl groups)-. Sodium Sulfate Dissolving Properties:

Water temperature. F Dissolving Properties 1 Comparative. No cake.

' Soft cake.

4 Hard cake.

Pursuant to the requirements of the patent statutes, the principle ofthis invention has been explained and exemplified in a manner so that itcan be readily practiced by those skilled in the art, suchexemplification including what is considered to represent the bestembodiment of the invention. However, it should be clearly understoodthat, within the scope of the appended claims, the invention may bepracticed by those skilled in the art, and having the benefit of thisdisclosure, otherwise than as specifically described and exemplifiedherein.

What is claimed is:

1. A dry-mixed, built detergent composition containing compacted sodiumtripolyphosphate and being readily soluble in water without caking underadverse dissolving conditions, essentially containing 20 to 90% of agranular compacted sodium tripolyphosphate having a density of 1.0g./cc. to 1.25 g./cc. and a particle size of about 16 to +100 mesh, saidcompacted sodium tripolyphosphate having uniformly distributed thereon2.5% to 7% of water, and the balance of said composition essentiallycontaining at least one of 0.5 to of a water-soiuble, non-soap organicsynthetic detergent from the group consisting of water-soluble anionicdetergents and water-soluble nonionic detergents, 0.5 to 50% of sodiumsilicate having a molar ratio of Na O to 510 of about 1:1 to 1:3.2, 0.5to 20% of a chlorocyanuric compound from the group consisting ofchlorocyanuric acids, an alkali metal or alkaline earth metal salt ofdichlorocyanuric acid and mixtures thereof, 0.5 to 50% of chlorinatedtrisodium phosphate, 0.5 to 50% of an alkali metal carbonate and 0.5 to60% of an inert inorganic filler.

2. The composition of claim 1 in which the sodium tripolyphosphate hasdistributed thereon 2.5% to 4% of water.

3. The composition of claim 1 in which the dry-mixed, built detergentcomposition is in the form of a tablet.

caking under adverse dissolving conditions, which essentially involvesdry-mixing 20 to of a granular compacted sodium tripolyphosphate havinga density of 1.0 g./cc. to 1.25 g./c c. and a particle size of about -16to mesh, said compacted sodium tripolyphosphate hawing uniformlydistributed thereon 2.5 to 7% of water, and the balance of saidcomposition which essentially contains at least one of 0.5 to 50% of awatersoluble, non-soap Organic synthetic detergent from the groupconsisting of water-soluble anionic detergents and water-solublenonionic detergents, 0.5 to 50% of sodium silicate having a molar ratioof Na O to SiO of about 1:1 to 123.2, 0.5 to 20% of a chlorocyanuriccompound from the group consisting of chlorocyanuric acids, an alkalimetal or alkaline earth metal salt of dichlorocyanuric acid and mixturesthereof, 0.5 to 50% of a chlorinated trisodium phosphate, 0.5 to 50% ofan alkali metal carbonate and 0.5 to 60% of in inert inorganic filler.

6. The method of claim 5 in which the sodium tripolyphosphate hasdistributed thereon 2.5% to 4% of water.

7. The method of claim 5 in which the dry-mixed, built detergentcomposition is compressed into tablets.

8. The method of claim 5 in which the dry-mixed, built detergentcomposition is granular.

References Cited UNITED STATES PATENTS 3,096,291 7/1963 Schauet' et al.25299 3,108,969 10/1963 Symes 252--99 3,233,967 2/1966 Schen 252- X3,247,123 4/1966 Schrager et al. 252-135 LEON D. ROSDOL, PrimaryExaminer.

M. WEINBLATT, Assistant Examiner.

1. A DRY-MIXED, BUILT DETERGENT COMPOSITION CONTAINING COMPACTED SODIUMTRIPOLYPHOSPHATE AND BEING READILY SOLUBLE IN WATER WITHOUT CAKING UNDERADVERSE DISSOLVING CONDITIONS, ESSENTIALLY CONTAINING 20 TO 90% OF AGRANULAR COMPACTED SODIUM TRIPOLYPHOSPHATE HAVING A DENSITY OF 1.0G./CC. TO 1.25 G./CC. AND A PARTICLE SIZE OF ABOUT -16 TO +100 MESH,SAID COMPACTED SODIUM TRIPOLYPHOSPHATE HAVING UNIFORMLY DISTRIBUTERDTHEREON 2.5% TO 7% OF WATER, AND THE BALANCE OF SAID COMPOSITIONESSENTIALLY CONTAINING AT LEAST ONE OF 0.5 TO 50% OF A WATER-SOLUBLE,NON-SOAP ORGANIC SYNTHETIC DETERGENT FROM THE GROUP CONSISTING OFWATER-SOLUBLE ANIONIC DETERGENTS AND WATER-SOLUBLE NONIONIC DETERGENTS,0.5 TO 50% OF SODIUM SILICATE HAVING A MOLAR RATIO OF NA2O TO SIO2 OFABOUT 1:1 TO 1:3.2, 0.5 TO 20% OF A CHLOROCYANURIC COMPOUND FROM THEGROUP CONSISTING OF CHLOROCYANURIC ACIDS, AN ALKALI METAL OR ALKALINEEARTH METAL SALT OF DICHLOROCYANURIC ACID AND MIXTURES THEREOF 0.5 TO50% OF CHLORINATED TRISODIUM PHOSPHATE, 0.5 TO 50% OF AN ALKALI METALCARBONATE AND 0.5 TO 60% OF AN INERT INORGANIC FILLER.